ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Lung Cancer. To see other pages, use the menu on the side of your screen. Think of that menu as a roadmap to this full guide.
Lung cancer affects more than 200,000 Americans each year. Although cigarette smoking is the main cause, anyone can develop lung cancer. Lung cancer is always treatable, no matter the size, location, whether the cancer has spread, and how far it has spread.
About the lungs
When a person inhales, the lungs absorb oxygen from the air and bring the oxygen into the bloodstream for delivery to the rest of the body. As the body’s cells use oxygen, they release carbon dioxide. The bloodstream carries carbon dioxide back to the lungs, and the carbon dioxide leaves the body when a person exhales. The lungs contain many different types of cells. Most cells in the lung are epithelial cells. Epithelial cells line the airways and make mucus, which lubricates and protects the lung. The lung also contains nerve cells, hormone-producing cells, blood cells, and structural or supporting cells.
About lung cancer
Lung cancer begins when cells in the lung change and grow uncontrollably, forming a mass called a tumor, a lesion, or a nodule. A lung tumor can begin anywhere in the lung. A tumor can be cancerous or benign. Once a cancerous lung tumor grows, it may or may not shed cancer cells. These cells can be carried away in blood or float away in the fluid, called lymph, that surrounds lung tissue. Lymph flows through tubes called lymphatic vessels that drain into collecting stations called lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes are located in the lungs, the center of the chest, and elsewhere in the body. The natural flow of lymph out of the lungs is toward the center of the chest, which explains why lung cancer often spreads there first. When a cancer cell moves into a lymph node or to a distant part of the body through the bloodstream, it is called metastasis.
Types of lung cancer
There are two major types of lung cancer: non-small cell and small cell.
Non-small cell lung cancer (NSCLC). NSCLC comes from epithelial cells and is the most common type. NSCLC may also be described based on the type of epithelial cell where the cancer starts. Adenocarcinoma starts in cells that produce mucus. Squamous or epidermoid carcinoma begins in the cells that line the airways. Large cell carcinoma begins in cells other than the two types described above.
Small cell lung cancer. Small cell lung cancer begins in the nerve cells or hormone-producing cells of the lung. The term “small cell” refers to the size and shape of the cancer cells as seen under a microscope.
It is important for doctors to distinguish NSCLC from small cell lung cancer because the two types of cancer are usually treated in different ways. The type of lung cancer, such as NSCLC or small cell, and stage of the disease (discussed later in the Stages  section) determine what type of treatment is needed.
Looking for More of an Overview?
If you would like additional introductory information, explore these related items. Please note these links take you to other sections on Cancer.Net:
- ASCO Answers Fact Sheet : Read a one-page fact sheet (available as a PDF) that offers an easy-to-print introduction to this type of cancer.
- ASCO Answers Guide : This 44-page booklet (available as a PDF) helps newly diagnosed patients better understand their disease and treatment options, as well as keep track of the specifics of their individual cancer care plan.
- Cancer.Net En Español: Read about lung cancer in Spanish . Infórmase sobre cáncer de pulmón en español .
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